Nickel electroplating electrolyte



United States Patent US. Cl. 20449 4 Claims ABSTRACT OF THE DISCLOSURE An aqueous acidic electrolyte for 'electrodepositing bright nickel comprising as brightener dimethylaminopropyne hydrochloride. The electrolyte may additionally contain various other additives such as sulfo-oxygen compounds and coumarin. Such a solution is more tolerant of zinc contamination.

This application is a continuation-in-part on application No. 423,309, filed Jan. 4, 1965, now abandoned.

This invention relates to bright nickel plating. The main object of the present invention is to provide ,a method of obtaining a reliable bright nickel coating. A' further "object is to obtain a nickel coating which is ductile insteadof being brittle as are many bright nickel coatings. Further objects of the invention are to reduce stress cracking of the coating and to achieve levelling, i.e. smooth coatings when the base surface is uneven.

According to the invention a method of bright nickel coating comprises adding dimethylaminopropync hydrochloride to the bath. Preferably this substance is used in the range of at least 0.005 but less than 0.2 gram per litre. We have found unexpectedly that in such concentration the nickel coating is ductile whereas greater concentrations produce brittle coatings. The best results are obtained in the range 0.005 to 0.2 gram per litre.

According to a preferred method the bath comprises an aqueous solution for use in bright nickel electroplating which contains (a) a sulpho-oxygen compound selected from mononuclear aromatic sulphonic, sulphinic acids and binuclear aromatic sulphonic acids, heterosulphonic acids, alkali metal, ammonium magnesium and nickel salts of said acids, (b) at least one nickel salt, (c) boric acid and (d) dimethylaminopropyne hydrochloride.

The sulpho-oxygen compounds are particularly useful in stress relief of the coatings.

To assist levelling there may be included a proportion of 2-propene-1-sulphonic acid sodium salt or sodium allyl bisulphite, or coumarin.

Examples of the sulpho-oxygen compounds that were used in conjunction with the dimethylaminopropyne hydrochloride and 2 propene-l-sulphonic acid, in the high boric acid-nickel solution are to be found in Table 1.

TABLE 1 (1) Mononuclear aromatic sulphonic acids, and alkali metal, ammonium, magnesium and nickel salts thereof.

C- H SO H (benzene monosulphonicacid) C H SO Na (sodium benzene monosulphonate) (C H SO Ni (nickel benzene monosulphonate) CH C H SO Na (sodium para-toluene monosulphonate) ClC H SO I-I (para-chlorobenzene sulphonic acid) ClC H SO Na (sodium para-chlorobenzene sulphonate) BrC H SO Na (sodium para-bromobenzene sulphonate) Cl C H SO H (1,2-dichlorobenzene sulphonic acid) Cl C H SO Na (1,2 to 2,5-dichlorobenzene sulphonate sodium salt) 3,546,081 Patented Dec. 8, 1970 C H CH=CHSO Na (sodium phenylethylene sulphonate) C H (SO H) (meta-benzene disulphonic acid) C H (SO Na) (sodium meta-benzene disulphonate) C H (SO Ni (nickel meta-benzene disulphonate) HOCOC H SO NH (ortho-sulphobenzoic acid monoammonium salt) H N%)H (SO H) (1-amino-2,5 benzene disulphonic ac1 H NC H SO H (ortho-aminobe'nzene sulphonic acid) (2) Mononuclear aromatic sulphinic acids, and alkali metal, ammonium, magnesium and nickel salts thereof.

C H SO Na (sodium benzene sulphinate) CH H H SO Na (sodium para-toluene sulphinate) (3) Monounclear aromatic sulphonamides and sulphonimides.

C H SO NH (benzene sulphonamide) CH C H SO NH (para-toluene sulphonamide) C H CONHSO (ortho-benzoic sulphimide) C H CH SO NH (benzyl sulphonamide) C H SO NHOH (benzene sulphydroxamic acid) CH C H SO N(CH (N,N dimethyl para-toluene sulphonamide) C H SO N(C H COOH) (N,N dicarboxyethyl benzene sulphonamide) (4) Binuclear aromatic sulphonic acids and alkali metal, ammonlum, magnesium, and nickel salts thereof.

C H SO H (Z-naphthalene monosulphonic acid) C H (SO Ni (1,5 or 2,7 naphthalene disulphonic acid nickel salt) C H (SO H) (naphthalene trisulphonic acid) C I- SO Na) (naphthalene trisulphonic acid trisodium sa t HSO C H C H SO H (diphenyl pp disulphonic acid) HOC H (SO H) (2-naphthol-3, 6-disulphonic acid) HOC H (SO Na (2-naphthol-3, 6-disulphonic acid sodium salt) H N.%; H (SO H) (1 naphthylamine-3, 6,8-trisulphonic Heterocyclic sulphonic acids and alkali metal, ammonrum, magnesium, and nickel salts thereof.

C.,H S.SO H (thiophene sulphonic acid) C H S.SO' Na (sodium thiophene sulphonate) C H. Igl).CH CH SO H (2-(4-pyridyl) ethyl sul honic Brilli an t nickel deposits may be obtained in accordance with this invention from electrolytes listed in Table 2.

TABLE 2 Bath 1 Bath 2 Nickel sulphate, Nl/SO47H2O 280 87 Nickel chloride, NiO126H2O 40 200 Sodium chloride, NaOl. Boric acid, H3BOa...., 56 56 Naphthalene trisulphon' acid sodium salt 'reihifa'tiir'F'o'I I II i "is Current density, amps sq./it 40-100 40-100 Dimethylamino-propyne hydrochloride 0. 12 0. 12 Orthobenzoic sulphimide sodium salt 1-2 1-2 2 propane-l sulphonic acid Sodium allyl bisulphite 0. 2 0. 2

3 EXAMPLE Add the following reactants to a stainless steel vessel and stir for 2 hours:

380 litres of water 59 kilos allyl alcohol 104 kilos sodium bisulphite Raise the temperature to 50 C. for /2 hour. Cool to 30 C. make and record addition of allyl alcohol and sodium bisulphite. Stir for 2 hours, raise temperature to 60 C. and maintain for 2 hours. Cool and filter.

The pH of the baths may be 3 to 5, e.g. 3.6.

The dimethyl amino propyne hydrochloride must be made before it is introduced into the bath solution or bath solution additive mixture. The same results are not obtainable merely by adding the propyne together with some hydrochloric solution to the bath or additive mixture. The hydrochloride is made by known methods, e.g. as follows:

40 kg. dimethylamino propyne calculated as anhydrous material and 10.5 kg. mains water or distilled water are mixed in a 150 l. enamelled vessel fitted with a stirrer. The solution is cooled to +5 C. and the pH adjusted to 2.9-3.2 with conc. hydrochloric acid (35.7%). The temperature should not rise above 10 C. during the addition of the acid. 49.5 kg. hydrochloric acid are required. The mixture is stirred for one hour. 100 kg. water-white dimethylamino propyne hydrochloride containing 40% dimethylaminopropyne as active substances are obtained.

The water content of the dimethylaminopropyne used for producing the hydrochloride is determined by the Karl Fischer method. The acid content of the hydrochloride acid is also determined. The quantity of 'water used depends on these two values.

I claim:

1. An acidic aqueous solution for use in bright nickel electroplating which includes nickel ions and at least .005 but not exceeding 0.2 gram per litre of the solution of dimethylaminopropyne hydrochloride.

2. An acidic aqueous solution for use in bright nickel electro-plating which contains (a) from 5 to grams per litre of a sulpho-oxygen compound selected :from the group consisting of mononuclear aromatic sulphonic acids, binuclear aromatic sulphonic acids, and heterocyclic sulphonic acids, and alkali metal, ammonium, magnesium, and nickel salts of said acids; (b) at least one nickel salt selected from the group consisting of nickel sulphate, nickel chloride, nickel formate, nickel fluoborate, and nickel sulphamate; (c) boric acid; and (d) from 0.005 to 0.2 gram per litre of dimethylaminopropyne hydrochloride.

3. A solution as claimed in claim 2, wherein the sulpho oxygen compound is 1:326 naphthalene trisulphonic acid.

4. A solution as claimed in claim 2, wherein the sulphooxygen compound is ortho benzoic acid sulphimide.

References Cited UNITED STATES PATENTS 3,002,904 10/ 1961 Foulke et al. 20449 3,006,822 10/1961 Todt 204-49 FOREIGN PATENTS 165,954 4/ 1954 Australia 204-49 858,718 1/1961 Great Britain 20449 GERALD L. KAPLAN, Primary Examiner 

